The subject invention relates generally to an improved damper assembly for a motor vehicle. More specifically, the subject invention relates to an adjustable damper for a motor vehicle.
Suspension dampers are used in combination with vehicle suspension systems to reduce the amount of vibration transmitted through a motor vehicle from such variables as, for example, potholes, rough road surfaces, and unbalanced tires. These dampers are typically adjusted to meet the requirements of a particular mass of the vehicle. Often, the vehicle will be used to transport a load that will significantly increase the mass being supported by the suspension system. This adversely affects the damping properties of the suspension damper as is evident by increased amounts of vibration transmitted through a vehicle when a heavy load is being transported.
A typical suspension damper includes a housing with a pumping cylinder axially aligned inside the housing defining a pumping chamber. A piston and rod is located in the pumping cylinder so that the piston moves in relation to movements or vibrations in the suspension system. Damping fluid fills the pumping cylinder around the piston and partially fills the area between the housing and the pumping cylinder, which acts as a reservoir. A barrier (or base valve) is located at the end of the pumping cylinder away from the rod that separates the interior of the pumping cylinder from the area between the pumping cylinder and the housing. The piston and the barrier are equipped with a system of valves and orifices such that when the suspension damper is reacting to a suspension move, damping fluid is forced to flow through these valves and orifices. The resistance of the damping fluid to flow through the valves and orifices causes the suspension damper to generate a force resisting the movement of the suspension, thus damping the movement. The damping characteristics of this type of damper, as described, are generally non-adjustable after being manufactured.
The valves and orifices used to control a suspension damper of this type are setup so that both the piston and base valve have some damping control during a compression stroke and an extension (rebound) stroke of the damper. However, during a compression stroke, most of the damping restriction is in the base valve, and during a rebound stroke, most of the damping restriction is in the piston. During a compression stroke, as the rod is pressed into the area of the pumping cylinder, damping fluid is forced through the base valve into the reservoir area and through the piston in a direction away from the base valve. During a rebound stroke, damping fluid is forced through the piston in a direction toward the base valve and is drawn into the pumping cylinder, from the reservoir, through the base valve. It should be noted that in both cases, most damping control exerted by these valves is applied to damping fluid flowing in a direction toward the base valve and to the reservoir.
One method used to provide external control to this type of damper uses an additional axial cylinder to provide an additional damping fluid flow path from a location over the piston and base valve to the reservoir. An externally controllable electric valve and an additional valve and orifice set are positioned to control and damp the additional flow. Working in parallel with the other fixed valve and orifice sets, this allows external control of the suspension damper performance. Electrically controlled systems such as this require separate control systems that add significant cost to a vehicle. It would be desirable to utilize an adjustable damper having an actuation member that does not require a controller to adjust the characteristics of a suspension damper.
The present invention is a suspension damper assembly for a vehicle suspension system. A pumping cylinder is axially aligned inside a housing and defines a pumping chamber. An intermediate cylinder defines an intermediate chamber with the pumping cylinder and an outer chamber with the housing. Suspension fluid flows in the area between the pumping cylinder and the intermediate cylinder. The area between the intermediate cylinder and the housing functions as a reservoir. A piston strokes inside the pumping chamber damping the vibration derived from the suspension system. A valve controls the distribution of fluid between the chambers thereby controlling the amount of vibration damping inside the pumping chamber.
The valve includes a spring actuated member to restrict the flow of fluid between the outer chamber and the intermediate chamber. A locator system is provided as a means of applying external control to the spring actuated member. The locator system includes a bellows disposed inside an air chamber, such that as pressure inside the air chamber is increased, the bellows constricts or becomes shorter. A projection from the end of the bellows extends out of the air chamber and contacts the spring actuated member, acting against the spring. When pressure in the air chamber is relatively high, the bellows is constricted and the bellows projection is withdrawn allowing the spring actuated member spring to locate the valve member to restrict flow. When the pressure in the air chamber is reduced, the bellows expands correspondingly. The bellows projection, working against the spring, moves the valve member and allows increased flow. By increasing the amount of flow to the intermediate chamber, the overall level of damping provided by the suspension damper is reduced. Connecting this device, as shown, to an air leveling system could provide damping control corresponding to vehicle load.
The present invention adjusts the damping properties of the suspension damper without utilizing a controller or a sophisticated electrical valve. This type of system could be applied such that air pressure, used in some suspensions to maintain vehicle attitude under varying loads, could be used to automatically adjust suspension damping, again compensating for the vehicle load. The simple mechanical concept utilizing air pressure from the suspension system is lest costly and more durable than the prior art electric and pneumatic designs.